1. Field of the Invention
The invention concerns a method of manufacturing a layered, stationary core, such as a core of a stator on an electrical motor.
2. Background Art
A stationary core, operational and productive as a coil for a magnetic pole, is commonly manufactured using a plurality of joined sections formed, as by a punching operation, from sheet material. The sections are stacked to form portions of a magnetic pole core around which wire is wound. After winding, the partial magnetic pole core portions are assembled into a circular shape and connected to complete the stationery core. Using this method, winding of the wire is facilitated but, in assembling the magnetic pole core portions to each other, a long time may be required.
For this reason, a method has been proposed recently whereby, core portions, made as described above, are connected to each other for relative movement. In this way, assembly of the core portions after winding is easily and effectively carried out. According to this method, as shown in FIGS. 7–9, magnetic pole sheet layers 10,12, shown in FIGS. 7 and 8, respectively, having first and second different configurations, are used. The first configuration magnetic pole sheet layer 10 has a plurality of arcuate yoke parts 14,14′,14″, each furnished with radially spaced depressions 16 and terminating at a radially inward location at a pole part 18. On one circumferential pointed end 20,20″ of each yoke part 14,14″, a connector 22,22″ is formed, each having a concave part 24,24″ on an upper side 26 and a convex part 28,28″ on a lower side 29.
The second configuration magnetic pole sheet layer 12, that is stacked with the first configuration magnetic pole sheet layer 10, has a plurality of arcuate yoke parts 30,30′,30″, corresponding to the yoke parts 14,14′,14″. The yoke parts 14,14′, 14″ are each furnished with radially spaced depressions 32 and terminate at a radial inward location at a pole part 34. Each yoke part 30,30′ has a pointed circumferential end 36,36′ pointing oppositely to the circumferential end 20,20″ on each yoke part 14,14″ on the first configuration magnetic pole sheet layer 10. At the ends 36,36′, a connector 38,38′ is formed having a concave part 40,40′ on an upper side 42 and a convex part 44,44′ on a lower side 46.
With this construction, the second configuration magnetic pole sheet layers 12 are formed and alternatingly stacked with the first configuration magnetic pole sheet layers 10 so that the convex parts 44,44′ of the connectors 38,38′ fit within the concave parts 24,24″ of the connectors 22,22″ of the first configuration magnetic pole sheet layer 10. As the magnetic pole sheet layers 10,12 are stacked, the depressions 16,32 nest. With this arrangement, the magnetic pole sheet layers 10,12 can be connected so that the stacked yoke parts 14,14′,14″, 30,30′,30″ can pivot freely back and forth relative to each other at the locations of the connectors 22,22″, 38,38′.
However, because the first and second configuration magnetic pole sheet layers 10,12 have yoke parts 14,14′,14″, 30,30′,30″ with oppositely pointing circumferential ends 20,20″, 36,36′, the layering process becomes complicated for each layering step.
Also, the formation of the concave 24,24″, 40,40′ and convex 28,28″, 44,44′ parts of the connectors 22,22″, 38,38′, as shown in FIG. 9, requires a punch 48 (FIG. 9) with a diameter D to advance towards a die element 49 furnished with openings 50 having a diameter D1 that is less than the diameter D. The punch 48 passes guidingly through a press plate 52, which sandwiches the sheet material 54, from which the yoke parts 14,14′,14″, 30,30′,30″ are formed, against the die element 49. In this case, if a thin metal laminate is being used for the sheet material, in constructing the first and second configuration magnetic pole sheet layers 10,12, it is difficult to stabilize the concave 24,24″, 40,40′ and convex 28,28″, 44,44′ parts. This instability at the connectors 22,22″, 38,38′ is a problem.